Chimpanzees are well known to be our closest non-human relatives, but the surprising extent to which they share cognitive abilities with human beings is still being discovered. Drs. Boysen and Berntson are investigating the numerical competence of chimpanzees. Their preliminary research with young animals has demonstrated numerical skills including rudimentary counting and addition. Further studies should contribute to our understanding of the similarities and differences in cognitive capabilities across species and toward clarifying those processes that may support numerical skills in non-human primates. Besides these contributions to basic scientific knowledge, these studies may yield sharper tests for and understanding of numerical competence in children and, more generally, provide a better understanding of non-verbal intelligence. Thus, the present project may provide insights into the cognitive abilities of language- impaired or otherwise developmentally-challenged children. Motor tagging (touching or pointing to items) during counting will be evaluated for its functional significance relative to similar behaviors of children in the early stages of learning to count. This study will clarify whether or not these behaviors, which appeared spontaneously in one animal, serve as an organizing strategy for keeping track of those items that have already been counted and those that remain to be counted. Another study will explore subtraction, by presenting the animals an array of 2 to 6 pieces of fruit, covering it, and then removing 1 to 4 items out of the animal's view. Early results suggest that the chimpanzees are able to indicate the remainder of the hidden fruit by selecting the correct Arabic numeral from among alternatives 0 to 5. An adult female chimpanzee with extensive prior training on a range of concepts, including a symbolic language system, will begin training with numbers, following the same procedures that were used with the young animals. At the same time, a computer- assisted testing apparatus will be developed to facilitate training and data-collection with adult chimpanzees.
